Most English-speaking Americans are familiar with the ways in which nicknames
and diminutives are formed in the U.S. Typically, the last syllable is removed
and sometimes the long e sound is appended to make it diminutive. For
example, "Joseph" is truncated to "Joe", and the long e sound is added
to form "Joey". Anglo-Saxon names often change the first letter of a
diminutive. Robert becomes Rob becomes Bob becomes Bobby; William becomes Will
becomes Bill becomes Billy; Richard becomes Rich becomes Rick becomes Dick.

Any American can easily identify that Dick is short for Richard, but that
convention is not at all obvious to the non-English speaker.